It was found that the T-helper and B cell functions decrease at a constant rate in mice from young-adulthood to old age. In contrast, the suppressor function increases at a relatively early age and remains elevated thereafter. We plan to depress the exaggerated suppressor function by prolonged treatment of the mice with anti-IJ serum, and to measure the effects of this treatment on the immune potential of aged mice. We also plan to assess the effects of long-term administration of transfer factor on the T-helper, T-suppressor and B-cell functions and on the longevity of aged mice. Preliminary experiments have shown that long-term administration of transfer factor preserves the immune potential of old mice. Finally, we will attempt to delay the onset of autoimmunity in NZB mice by administration of non-T suppressor cells induced by cyclophosphamide which we believe are involved in the establishment and maintenance of immune tolerance.